Gasification apparatus and method

ABSTRACT

A gasification system is disclosed having a combustor, a scrubber, a finisher, and optionally a recycler. A carbonaceous fuel is partially combusted in the combustor to generate a combustible gas. An improved ash support and removal system reduces clogging and other problems in the combustor. The combustible gas passes through the scrubber to remove matter such as tar and oil and to undergo preliminary catalytic chemical reactions. The scrubbed gas passes through a hybrid blower to the finisher. Final catalytic chemical reactions occur in the finisher, and wood chips or other filters may also be used in the finisher to provide a relatively clean, dry, combustible gas. Wastewater and other waste products from the scrubber and finisher are captured in the recycler and returned to the combustor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of co-pending U.S. patentapplication Ser. No. 10/911,386, filed Aug. 4, 2004, which claimsbenefit of U.S. Provisional Patent Application Ser. No. 60/492,363,filed Aug. 4, 2003. Each of the aforementioned related patentapplications is herein incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to gasification and, more particularly, to aflexible gasification apparatus and method that provides combustiblegases having high heating values while avoiding pitfalls of priorattempts at gasification.

2. Description of the Related Art

Gasification has generally been known for years. In gasification, acarbonaceous fuel source is partially combusted to produce a combustiblegas, synthesis gas, or syngas. The combustible gas is then combusted toproduce work. The combustible gases produced by gasification may findany number of uses, including but not limited to supplying heat,powering a motor, or producing electricity. Gasification provides manyadvantages, such as allowing fuels having relatively low heating valuesto be used, allowing waste products to be used to produce work, and,similarly, reducing the amount of waste material that must be sent tolandfills. Despite these obvious advantages, gasification has met withonly limited success, because gasification systems have typically beenplagued by a number of disadvantages or difficulties. For example, theheating values of gases produced using prior art systems have tended tofluctuate to an undesirable degree, particularly when a variety of fuelsources or fuel sources of varying compositions have been used.Similarly, it has also proven difficult to consistently produce gaseshaving sufficiently high heating values. Separating particulate matterfrom the produced gas has proven problematic. Similarly, it has provendifficult to produce sufficiently clean gases having sufficiently lowamounts of particulate matter as well as sufficiently low amounts ofpollutants such as such as sulfur dioxide (SO₂), nitrogen oxides(NO_(x)), carbon monoxide (CO), volatile organic compounds (VOC),ammonia (NH₃), hydrogen chloride (HCl), and other chlorides.Environmentally sound disposal of wastewater generated by such systemshas also presented difficulties. Further still, the presence of water orother liquids in the combustible gas has made it difficult or impossibleto use blowers for moving the combustible gases without creatingundesirable levels of wear and tear on the blowers.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a flexiblegasification apparatus and method that provides combustible gases havinghigh heating values while avoiding pitfalls of prior attempts atgasification.

It is a further object of the present invention to provide an apparatusand method of the above type that can easily handle a wide variety ofcarbonaceous fuel sources or combinations of fuel sources.

It is a further object of the present invention to provide an apparatusand method of the above type that produces a high value heating gashaving low amounts of particulate matter and other pollutants.

It is a further object of the present invention to provide an apparatusand method of the above type that requires little or no wastewaterdisposal.

It is a still further object of the present invention to provide anapparatus and method of the above type that captures a relatively highfraction of the potential heating value of the fuel sources.

It is a still further object of the present invention to provide anapparatus and method of the above type that safely and cleanly consumesa wide variety of agricultural and industrial byproducts, including butnot limited to animal waste and wood pulp sludge.

It is a still further object of the present invention to provide anapparatus and method of the above type that is less prone to cloggingproblems typically associated with ash removal.

It is a still further object of the present invention to provide anapparatus and method of the above type that may easily process a widevariety of combinations of solid, semi-solid, and liquid fuels.

It is a still further object of the present invention to provide anapparatus and method of the above type that can safely and efficientlyhandle and dry relatively wet combustible gases.

It is a still further object of the present invention to provide anapparatus and method of the above type that uses a rugged, hybrid blowerthat can safely and efficiently handle both dry and relatively wetcombustible gases.

Toward the fulfillment of these and other objects and advantages, thesystem of the present invention comprises a combustor, a scrubber, afinisher, and optionally a recycler. A carbonaceous fuel is partiallycombusted in the combustor to generate a combustible gas. An improvedash support and removal system reduces clogging and other problems inthe combustor. The combustible gas passes through the scrubber to removematter such as tar and oil and/or to undergo preliminary catalyticchemical reactions. The scrubbed gas passes through a hybrid blower tothe finisher. Final catalytic chemical reactions occur in the finisher,and wood chips or other filters may also be used in the finisher toprovide a relatively clean, dry, combustible gas. Wastewater and otherwaste products from the scrubber and finisher may be captured in therecycler and returned to the combustor.

BRIEF DESCRIPTION OF THE DRAWINGS

The above brief description, as well as further objects, features andadvantages of the present invention will be more fully appreciated byreference to the following detailed description of the presentlypreferred but nonetheless illustrative embodiments in accordance withthe present invention when taken in conjunction with the accompanyingdrawings, wherein:

FIG. 1 is a flow diagram of a system for practicing the presentinvention;

FIG. 2 is a side elevation, schematic view of a combustor for practicingthe present invention;

FIG. 3 is an overhead, schematic view of a blower for practicing thepresent invention; and

FIG. 4 is a side elevation view of an impeller for practicing thepresent invention.

DETAILED DESCRIPTION

Referring to FIG. 1, the reference numeral 10 refers in general to agasification system for practicing the present invention. The system 10will typically comprise a combustor 12, a scrubber 14, and a finisher16, and may also include a recycler 18. The system 10 principallyconsists of preferably a combustor 12 and a finisher 16, more preferablya combustor 12, a scrubber 14, and a finisher 16, and most preferably acombustor 12, a scrubber 14, a finisher 16, and a recycler 18. Thecombustor 12, scrubber 14, finisher 16, and recycler 18 may include anytype of reaction vessel.

Referring to FIG. 2, the combustor 12 has an upper, outer wall portion20 and a lower base portion 22. The combustor 12 is preferably open,more preferably closed, at the top and is preferably configured as adowndraft combustor, more preferably as an updraft combustor. A feedline, conduit, or fuel auger 24 is disposed above the combustor 12 toprovide a carbonaceous fuel source. Another feed line 26 may also beprovided to recycle material from other portions of the system 10 asdiscussed in more detail below. Additional feed lines may also be used,for example, to provide different types of solid, semi-solid, and liquidfuel sources. An inner wall 28 is disposed within the combustor 12 andis connected to the combustor 12 to form an inner chamber 30 and anouter chamber 32. A lower portion of the inner wall 28 defines anopening 34. An ash support member 36 is affixed to a lower portion ofthe inner wall 28 by rigid members 38 so that the ash support member 36is disposed a distance below the opening 34. The outer periphery of theash support member 36 is relatively free from obstructions about thevast majority of the outer periphery, providing relatively open sidepassageways between the inner wall 28 and the ash support member 36.This allows ash to spill from the ash support member 36 preferably overat least approximately 80 percent of the outer periphery of the ashsupport member 36, more preferably over at least approximately 90percent of the outer periphery of the ash support member 36, and mostpreferably over at least approximately 95 percent of the outer peripheryof the ash support member 36.

A gas injection ring 40 is affixed to the inner wall 28 and is disposedat a medial point of the inner chamber 30. Openings 42 in the inner wall28 provide a flow path for gas, such as air or an air and fuel mixture,to pass from a plenum 44 formed by the ring 40 into the inner chamber30. A conduit or gas manifold 46 extends through the outer wall 20 ofthe combustor 12 and is operably connected to the ring 40. The conduitor gas manifold 46 is connected to an air source and is preferablyconnected to a fuel source, such as a source of natural gas, liquefiedpetroleum gas (LPG or LP gas), or propane (C₃H₈). As seen in FIG. 1, arecycle line 48 may also be provided to return a portion of thecombustible gas generated by the system 10. An igniter 50, such as aspark plug igniter, is preferably disposed in the conduit or gasmanifold 46 adjacent to the combustor 12, more preferably disposedinside a partial shield to prevent particles from bridging the sparkplug gap, with said shield disposed in the conduit or gas manifold 46adjacent to the combustor 12. One additional igniter, partial shield,and branch of gas manifold 46 may be optionally (and is preferably)disposed diametrically opposite igniter 50 to improve combustionuniformity within combustor 12.

As seen in FIG. 2, a fuel agitator, such as fuel stirring member 52, isprovided in the inner chamber 30. The fuel stirring member 52 ispreferably disposed above the opening 34 and is more preferably disposedabove the ring 40. Similarly, an ash agitator or combustion bed stirrersuch as ash stirring member or combustion bed stirrer 54 is providedinside the combustor 12, below the ring 40 and above the ash supportmember 36. Another ash agitator such as ash stirring member 55 isprovided inside the combustor 12 below the ash support member 36.Coaxial shafts 56 and 58 extend upward from the stirring members 52, 54,and 55 to or above an upper portion of the combustor 12. Motors 60 and62 are operably connected to the shafts 56 and 58 for rotating theshafts and stirring members 52, 54, and 55.

Hollow shaft 58 is rotated by motor 60 and is preferably connected toboth stirring members 52 and 54, and more preferably connected tostirring member 52 but not to stirring member 54. Solid shaft 56 isrotated by motor 62 and is preferably connected to stirring member 55but not to stirring member 54, but more preferably connected to bothstirring member 54 and stirring member 55. Stirring members 52, 54, and55 are most preferably attached individually to separate coaxial shaftsthat are individually rotated by separate motors.

The frustoconical, lower base portion 22 of the combustor 12 extendsbelow the ash support member 36. An opening is provided at the bottom ofthe lower base portion 22 to allow ash to pass from the combustor 12 toan ash removal system 64, such as an auger drive for solids transfer. Aconduit 66 is provided through the outer wall of the combustor 12 in anupper portion of preferably the outer chamber 32, more preferably theinner chamber 30 to provide a path for combustible gases generatedwithin the combustor 12 to pass from the combustor 12.

A fuel level sensor 68 is provided in the inner chamber 30, preferablyabove the opening 34, more preferably above the ring 40, and mostpreferably above the fuel agitator 52. The fuel level sensor 68 isoperably coupled with the feed line or fuel auger 24 to automate theprocess of maintaining fuel at a desired level within the inner chamber30. An ash level sensor 70 is disposed within the combustor 12,preferably below the opening 34, more preferably below the ash agitatoror combustion bed stirrer 54, and most preferably below the ash supportmember 36. The ash level sensor 70 is operably coupled with the ashremoval system 64 to automate the process of maintaining ash at adesired level within the combustor 12. It is of course understood thatthe combustor 12 may take any number of sizes, shapes, andconfigurations. It is also understood that the combustor 12 need not beclosed at the top and need not be an updraft combustor 12.

Referring to FIG. 1, conduit 66 connects the combustor 12 with thescrubber 14, providing a flow path into preferably an upper portion,more preferably a lower portion of the scrubber 14. The scrubber 14preferably contains one or more filters (including, but not limited to,ferrous or non-ferrous metals, precious metals, ceramics, minerals,liquids, plastics, fibrous or non-fibrous materials, wood chips, organicor inorganic materials, porous or non-porous materials, natural orartificial materials, absorbents or adsorbents, diatomaceous earth,mixtures or combinations of these and other materials, or any otherfilter known to those skilled in the art). The scrubber 14 morepreferably contains one or more filters and one or more catalysts(including, but not limited to, ferrous or non-ferrous metals, preciousmetals, ceramics, minerals, liquids, plastics, fibrous or non-fibrousmaterials, wood chips, organic or inorganic materials, porous ornon-porous materials, natural or artificial materials, absorbents oradsorbents, diatomaceous earth, mixtures or combinations of these andother materials, or any other catalyst known to those skilled in theart). A pump 72 is preferably provided to pass liquid, for example waterwith impurities therein, through a feed line 74 into a preferably upperportion, more preferably lower portion, of the scrubber 14 andpreferably through sprayers. A liquid return line 76 is preferablyconnected to a lower portion of the scrubber 14 for returning liquid tothe pump 72 for reuse within the scrubber 14. A feed line or conduit 78may also be provided for providing preferably gas from combustor 12,more preferably gas and liquids from combustor 12, most preferably gasand liquids from combustor 12 and recirculated liquid to scrubber 14.Wash or recirculation lines 80 may be provided for intermittent use asdescribed below. Scrubbed gas exits through conduit 82 that is disposedat a preferably lower, more preferably upper portion of the scrubber 14.A skim line 84 is preferably provided at a lower portion of the scrubber14, and a blow down line or conduit 86 is provided at the bottom of thescrubber 14. A level sensor 88, such as a float switch, is preferablydisposed in the scrubber 14 for maintaining liquid levels within thescrubber 14 at desired levels. It is of course understood that thescrubber 14 may take any number of shapes, sizes, and configurations,and that any number of different filter media or catalysts or differentcombinations of filter media and catalysts may be used in scrubber 14.

Conduit 82 passes from the scrubber 14 to blowers 90. As best seen inFIG. 3, the blowers 90 are heavy duty hybrids that combine desirablefeatures of blowers designed for moving gases and pumps designed formoving liquids. Walls forming the impeller housing 92 have a wallthickness of preferably approximately 3/4 inch, more preferablyapproximately 5/8 inch. A sealing member 94, such as a gasket, is usedto create an airtight and watertight seal between the walls forming theimpeller housing 92. Referring to FIG. 4, the impeller blades 96 arepreferably straight, but are more preferably curved, and are thickerthan impeller blades of common blowers designed for moving gases,preferably approximately 50 percent thicker. Referring back to FIG. 3, apacking gland 98, similar to a packing gland used in a water pump, isused to provide a shaft 100 seal. Additional sets of bearings 102 arealso preferably used in connection with the impeller shaft 100. It ispreferred to use at least two sets of bearings 102. Referring to FIG. 1,conduit 104 passes from the blowers 90 to the finisher 16, providing aflow path into preferably a lower portion, but more preferably an upperportion, of the finisher 16. It is of course understood that the blowers90 may be disposed at any number of locations in the system 10 and thatthe blowers 90 may take any number of different sizes, shapes, andconfigurations. It is also understood that, although not preferred,conventional blowers may be used.

The finisher 16 preferably contains one or more filters (including, butnot limited to, ferrous or non-ferrous metals, precious metals,ceramics, minerals, liquids, plastics, fibrous or non-fibrous materials,wood chips, organic or inorganic materials, porous or non-porousmaterials, natural or artificial materials, absorbents or adsorbents,diatomaceous earth, mixtures or combinations of these and othermaterials, or any other filter known to those skilled in the art). Thefinisher 16 more preferably contains one or more filters and one or morecatalysts (including, but not limited to, ferrous or non-ferrous metals,precious metals, ceramics, minerals, liquids, plastics, fibrous ornon-fibrous materials, wood chips, organic or inorganic materials,porous or non-porous materials, natural or artificial materials,absorbents or adsorbents, diatomaceous earth, mixtures or combinationsof these and other materials, or any other catalyst known to thoseskilled in the art). Conduit 106 passes from preferably an upperportion, more preferably a lower portion, of the finisher 16 to providea flow path for the scrubbed and finished combustible gas. Additionalconduits 108, 48, and 110 are also provided for passing the scrubbed,finished combustible gas to flare, to recycle, and for further uses. Aconduit 112 passes from a lower portion of the finisher 16 for removingwastewater and other matter that condenses or is removed from the gas asit passes through the finisher 16. It is understood that the finisher 16may take any number of shapes, sizes, and configurations and that anynumber of different filter media or catalysts or different combinationsof filter media and catalysts may be used in finisher 16.

Conduits 84, 86, 112, and 114 preferably connect the scrubber 14 andfinisher 16 to a recycler 18, providing a flow path into an upperportion of the recycler 18. Return line or conduit 116 preferably passesfrom a lower portion of the recycler 18 to pump 118, and line 26preferably passes from pump 118 to combustor 12. A recirculation line120 is preferably provided for diverting a portion of the liquid fromthe return line 26 back to the recycler 18. A level sensor 122, such asa float switch, is preferably disposed in the recycler 18 formaintaining liquid levels within the recycler 18 at desired levels. Itis understood that the recycler 18 may take any number of differentshapes, sizes, and configurations.

In operation, feed line or fuel auger 24 provides a solid or semi-solidcarbonaceous fuel to the combustor 12. As seen in FIG. 2, the solid orsemi-solid fuel drops through the inner chamber 30, accumulates on theash support member 36, and builds up within the inner chamber 30 to alevel above the ring 40 and then above the fuel stirring member 52. Asseen in FIG. 1, an oxygen source, such as air, is provided preferablyvia conduit 124, more preferably via conduit 126 instead, and analternate fuel source is provided preferably via conduit 126, morepreferably via conduit 124 instead. Referring to FIG. 2, the air andalternate fuel are mixed inside conduit or gas manifold 46, ignited byigniter 50, and pass through the ring 40 and into the inner chamber 30.The burning air and alternate fuel mixture ignites the carbonaceous fuelwithin the inner chamber 30. As the carbonaceous fuel sources passdownward within the inner chamber 30, the carbonaceous fuel sources areat least partially combusted to produce, among other materials, ash anda combustible gas. Fuel stirring member 52 keeps the different fuelsources blended and reduces or prevents channeling, bridging, clumping,voids, and similar problems.

Ash passes through opening 34 and collects on ash support member 36. Theash stirring member or combustion bed stirrer 54 prevents ash build upby moving the collecting ash preferably outward so that the ash spillsor passes from the outer periphery of the ash support member 36, morepreferably moving the collecting ash downward so that the ash spills orpasses through perforations in ash support member 36, or most preferablymoving the collecting ash both outward from the outer periphery of ashsupport member 36 and downward through perforations in ash supportmember 36 to fall down to the lower base portion 22 of the combustor 12.Other than the ash stirring member or combustion bed stirrer 54 andsupport members 38, the area between the opening 34 of the inner wall 28and the top surface of ash support member 36 is substantiallyunobstructed to provide a ready path for ash removal, free fromobstructions and sources of clogging such as grates or mesh materials.In that regard, the support members 38 connect the ash support member 36to the inner wall 28 in a manner that allows ash to spill from the ashsupport member 36 preferably over at least approximately 70 percent ofthe outer periphery of the ash support member 36, more preferably overat least approximately 80 percent of the outer periphery of the ashsupport member 36, and most preferably over at least approximately 90percent of the outer periphery of the ash support member 36.

Ash that accumulates in the lower base portion 22 of the combustor 12passes through an opening in the bottom of the combustor 12 and isremoved by an ash removal system 64, such as by an auger or screw drive.The ash auger drive 64 is operably coupled with ash level sensor 70 tomaintain the ash in the combustor 12 below a desired amount. The ashremoved from the combustor 12 will typically be a salable product. Forexample, the ash might be suitable for sale as fertilizer, soilstabilizer, filter material, and/or as an extender for mortar, concrete,or road material, among other uses.

The fuel level sensor 68 is operably coupled with the solid orsemi-solid fuel feed line or fuel auger 24 to maintain solid orsemi-solid fuel within a desired height range within the inner chamber30. The desired height range will vary depending upon a number offactors, including but not limited to the properties of the solid orsemi-solid fuel. It is typically desirable to maintain the solid orsemi-solid fuel level within the inner chamber 30 at the lowest possiblelevel while still maintaining an adequate seal, preferably to preventproducts of combustion from escaping through the top of the combustor 12and/or to help control the degree of partial combustion within innerchamber 30. The level desired will vary with factors such as the densityand moisture content of the solid or semi-solid fuel. For example, thedesired level for a solid or semi-solid fuel comprised primarily ofchicken litter (including, but not limited to, chicken waste products,absorbents such as rice hulls or wood chips, or any combination of theseand similar or related materials) will tend to be higher than thedesired level for a solid or semi-solid fuel comprised primarily of woodpulp or paper mill sludge, and the desired level for a solid orsemi-solid fuel comprised primarily of wood pulp sludge will tend to behigher than the desired level for a solid or semi-solid fuel comprisedprimarily of sanding or wood dust. In a typical operation in which thesolid or semi-solid fuel is comprised primarily of chicken litter, thelevel of solid or semi-solid fuel within the inner chamber 30 ispreferably maintained at a height of approximately 8 inches toapproximately 10 inches above the ring 40. Similarly, in an operation inwhich the solid or semi-solid fuel is comprised primarily of wood pulpsludge, the level of solid or semi-solid fuel within the inner chamber30 is preferably maintained at a height that is only slightly above thering 40. Also, in an operation in which the solid or semi-solid fuel iscomprised primarily of sanding or wood dust, the level of solid orsemi-solid fuel within the inner chamber 30 is preferably maintained ata height that is approximately even with or slightly below the ring 40.

The blowers 90 draw gaseous products of combustion preferably downward,more preferably upward, through the combustor 12 so that they passthrough the opening 34 in the inner wall 28 and upwardly throughpreferably the outer chamber 32, more preferably the inner chamber 30before passing through conduit 66. Referring to FIG. 1, combustible gasfrom the combustor 12 enters preferably an upper portion, morepreferably a lower portion, of the scrubber 14 and passes upward towardconduit 82. Pump 72 circulates liquid, for example water with impuritiestherein, to the scrubber 14. Liquid enters the scrubber 14 throughconduit 74, passes preferably through sprayers, and contacts thecombustible gas. The liquid cools and scrubs the combustible gas,removing matter from the combustible gas including tar, oil, andparticulate matter. The liquid level in the scrubber 14 is maintained ata desired level so that tar, oil, and similar matter may be removed fromthe scrubber 14 preferably via the skimmer line 84. Particulate matterand other components that settle to the bottom of the scrubber 14 areperiodically removed via blow down line or conduit 86. Valves 128 arealso opened preferably periodically so that the pump 72 may circulateliquid through wash lines 80 and through conduits 66, 82, and 104 forcleaning. From time to time, valve 130 may be opened so that the liquidin scrubber 14 may also be drained through line 86 and preferablyreplaced with liquid from line 78. Filters in scrubber 14 primarilyremove liquids from the gas. Catalysts in scrubber 14 primarily improvethe chemical composition of the gas.

The scrubbed combustible gas exits the scrubber 14 through line 82,passes through blowers 90, and is driven through finisher 16. As itexits the scrubber 14, the gas may also be passed through afilter/knock-out pot, before being passed to the blowers 90. Wood chipsor other filters in the finisher 16 dry the gas and remove additionalamounts of particulate matter and other pollutants. Wastewater and othermatter that are removed from the combustible gas and that are notabsorbed by the wood chips or other filters fall to the bottom of thefinisher 16 and are removed via line 112. Filters in finisher 16primarily remove liquids from the gas. Catalysts in finisher 16primarily improve the chemical composition of the gas. Scrubbed,finished combustible gas exits the finisher 16 via line 106. From therethe combustible gas is flared via line 108, returned to the reactionchamber via line 48, or sent to other uses via line 110. During theinitial start-up phase, the combustible gas is flared until it isdetermined that gas is being produced at a desired quantity and quality.Once the start-up phase is complete, the combustible gas will primarilybe passed via line 110 to produce work or for further uses elsewhere.For example, the combustible gas might be combusted to supply heat to aprocess or might be combusted within a motor or turbine to produce workor to generate electricity. As additional examples, the combustible gasproduced by the system 10 may be used in brooder heaters in poultryhouses, in internal combustion engines, and in boilers. In fact, thecombustible gas generated by the present system 10 compares quitefavorably with natural gas, often being cleaner while having comparableor higher heating values. The heating values of the combustible gasproduced will vary depending upon a number of factors, such as the type,composition, and moisture content of the carbonaceous fuel provided, butthe heating values of the combustible gas produced will typically be ator near 550 British Thermal Units (BTUs) per cubic foot. Accordingly,combustible gas produced using the present system 10 is a good candidatefor use in any situation that currently uses natural gas, liquefiedpetroleum gas (LPG or LP gas), or propane.

Depending upon the properties of the carbonaceous fuels being suppliedto the combustor 12, such as the moisture content, a portion of thecombustible gas may be returned to the combustor 12 via line 48 tosupply additional fuel to aid in the partial combustion of thecarbonaceous fuel. The combustible gas supplied via line 48 may serve asa complete or partial replacement for the alternate fuel source suppliedto the combustor 12, preferably via line 126, more preferably via line124. Returning the combustible gas to the reaction chamber 12 offers anumber of advantages. For example, it saves on alternate fuel costs thatmight otherwise be required to maintain the desired combustion in thecombustor 12.

Lines 86, 84, 112, and 114 pass from the scrubber 14 and the finisher 16to recycler 18. These lines 86, 84, 112, and 114 pass wastewater, excessliquid from wet fuel components, tar, oil, particulate matter, and otherremoved substances to an upper portion of the recycler 18. Thesecomponents pass from the recycler 18, preferably via line 116 and pump118, via line 26 back to the combustor 12, where they are fed into anupper portion of the combustor 12. A portion of these components ispreferably diverted via line 120 and returned to the recycler 18 to helpstir or agitate the contents of the recycler 18. Returning thewastewater and other components to the combustor 12 provides a number ofadvantages. For example, the wastewater scavenges additional, residualcarbon from the ash as the liquid is broken down. This provides forbetter recovery of the heating value from the carbonaceous fuel andeliminates or drastically reduces the need to dispose of wastewater.

The system 10 may be used to process a wide variety of carbonaceousfuels, as well as combinations thereof. The spacing between the ashsupport member 36 and the opening 34 of the inner wall 28, as well asthe relatively unobstructed side openings there, allow a wide assortmentof solid or semi-solid fuels to be used without fear of clogging.Possible carbonaceous fuels include, but are not limited to, materialssuch as chicken litter, other animal waste, municipal solid orsemi-solid waste, glued woods (such as plywood and press board), papermill or wood pulp sludge (including sludge with a moisture content of65% or higher), wood or yard waste, agricultural waste, shredded tires,and mixtures or combinations of these and other carbonaceous materials.Liquid carbonaceous fuels may also be added, including but not limitedto waste motor oil and cooking oil. Adding these liquid carbonaceousfuels can markedly increase the heating value of the combustible gasproduced.

In one particular embodiment, the system 10 is approximately 6 feetwide, approximately 10 feet long, and approximately 7.5 feet tall. Thisparticular embodiment of system 10 gasifies approximately eighty (80)pounds of chicken litter per hour, requires no auxiliary fuel afterstartup, uses only about three (3) kilowatt-hours of electricity,produces over 3.5 million BTUs per hour of combustible gas, and producesonly about four (4) pounds per hour of mineral ash, generating no othersolid waste, no liquid waste, and no gaseous waste.

The following emissions test examples illustrate that the gasificationsystem 10 of the present invention can produce combustible gas that isenvironmentally friendly while processing solid or semi-solidcarbonaceous fuels that previously posed serious landfill issues.

EXAMPLE 1

An emissions test was conducted on combustible gas generated by thesystem 10 while combusting chicken litter. A sample run of 60 minutes induration was performed. Testing was performed in accordance with themethods detailed in 40 Code of Federal Regulations (CFR), Part 60,Appendix A. The flow, based on the lowest recordable flow, had avelocity of 6.77 feet per second, and the sample collected had a volumeof 41.42 dry standard cubic feet. The results of the emissions testingare summarized in Table 1 below. TABLE 1 Emissions Substance (lbs/hr)Particulate Matter (based on lowest detectable flow rate) 0.003 VOC asPropane (corrected for moisture) 0.137 Nitrogen Oxides as NO₂ 0.001Carbon Monoxide 0.003 Sulfur Dioxide 0.096 Ammonia 0.033 HCl 0.008Chloride 0.005

EXAMPLE 2

An emissions test was conducted on combustible gas generated by thesystem 10 while combusting paper mill sludge. A sample run of 60 minutesin duration was performed. Testing was performed in accordance with themethods detailed in 40 CFR, Part 60, Appendix A. The flow, based on thelowest recordable flow, had a velocity of 6.53 feet per second, and thesample collected had a volume of 40.60 dry standard cubic feet. Theresults of the emissions testing are summarized in Table 2 below. TABLE2 Emissions Substance (lbs/hr) Particulate Matter (based on lowestdetectable flow rate) 0.0014 VOC as Propane (corrected for moisture)0.014 Nitrogen Oxides as NO₂ 0.013 Carbon Monoxide 0.051 Sulfur Dioxide0.017

Other modifications, changes and substitutions are intended in theforegoing, and in some instances, some features of the invention will beemployed without a corresponding use of other features. For example, theconfiguration of the ash support member 36 may be used in combinationwith any number of different gasification systems, regardless of whethersuch systems also use other features of the present invention, and mayalso find uses in systems other than gasification systems. Similarly,the wastewater return features of the present invention may be used incombination with any number of different gasification systems,regardless of whether such systems also use other features of thepresent invention, and may also find uses in systems other thangasification systems. Further, the wood chip filtering or other filtersor catalysts of the present invention may be used in combination withany number of different gasification systems, regardless of whether suchsystems also use other features of the present invention, and may alsofind uses in systems other than gasification systems. Further still, thehybrid blower 90 design of the present invention may be used incombination with any number of different gasification systems,regardless of whether such systems also use other features of thepresent invention, and may also find uses in systems other thangasification systems. Of course, quantitative information is included byway of example only and is not intended as a limitation as to the scopeof the invention. Accordingly, it is appropriate that the invention beconstrued broadly and in a manner consistent with the scope of theinvention disclosed.

1. A method, comprising: (1) at least partially combusting acarbonaceous fuel to produce a combustible gas; (2) passing saidcombustible gas through one or more first filters to produce a scrubbedgas; (3) passing said scrubbed gas through one or more second filters toproduce a finished gas; and (4) after step (3), combusting said scrubbedand finished gas.
 2. The method of claim 1, wherein step (1) comprises:at least partially combusting said carbonaceous fuel to produce saidcombustible gas, said carbonaceous fuel comprising chicken litter. 3.The method of claim 1, wherein step (1) comprises: at least partiallycombusting said carbonaceous fuel to produce said combustible gas, saidcarbonaceous fuel comprising wood pulp sludge.
 4. The method of claim 1,wherein: step (1) comprises at least partially combusting saidcarbonaceous fuel in a combustor to produce said combustible gas; andstep (2) comprises passing said combustible gas through said one or morefirst filters in a scrubber to produce said scrubbed gas; and furthercomprising passing wastewater from said scrubber to said combustor. 5.The method of claim 1, wherein: step (1) comprises at least partiallycombusting said carbonaceous fuel in a combustor to produce saidcombustible gas; and step (3) comprises passing said scrubbed gasthrough said one or more second filters in a finisher; and furthercomprising passing wastewater from said finisher to said combustor. 6.The method of claim 1, wherein: step (3) comprises passing said scrubbedgas through said one or more second filters in a finisher; and furthercomprising: passing wastewater from said finisher to said combustor. 7.The method of claim 1, wherein: step (1) comprises at least partiallycombusting said carbonaceous fuel in a combustor to produce saidcombustible gas; step (2) comprises passing said combustible gas throughsaid one or more first filters in a scrubber to produce said scrubbedgas; and step (3) comprises passing said scrubbed gas through said oneor more second filters in a finisher; and further comprising: passingwastewater from said scrubber to a recycler; passing wastewater fromsaid finisher to said recycler; and passing said wastewater from saidscrubber and said wastewater from said finisher from said recycler tosaid combustor.
 8. The method of claim 1, wherein the one or more firstfilters comprise one or more catalysts.
 9. The method of claim 1,wherein the one or more first filters comprise one or more liquids. 10.A method, comprising: (1) at least partially combusting a carbonaceousfuel in a combustor to produce a combustible gas; (2) passing saidcombustible gas to a scrubber; (3) passing said combustible gas throughone or more filters within said scrubber; and (4) passing a firstportion of the one or more filters from said scrubber to said combustor.11. The method of claim 10, wherein step (3) comprises: passing saidcombustible gas through said one or more filters within said scrubber,said one or more filters comprising water.
 12. The method of claim 10,wherein step (3) comprises: passing said combustible gas through the oneor more filters within said scrubber to remove matter from saidcombustible gas, said matter comprising tar and oil; and furthercomprising: passing said tar and oil from said scrubber to saidcombustor.
 13. The method of claim 10, further comprising: passing saidcombustible gas from said scrubber to a finisher; and passing a wasteliquid from said finisher to said combustor.
 14. The method of claim 10,wherein step (4) comprises: passing said first portion of said liquidfrom said scrubber to a recycler; and passing said first portion of saidliquid from said recycler to said combustor.
 15. The method of claim 14,wherein step (3) comprises: passing said combustible gas through the oneor more filters within said scrubber to remove matter from saidcombustible gas, said matter comprising tar and oil; and furthercomprising: passing said tar and oil from said scrubber to saidrecycler; and passing said tar and oil from said recycler to saidcombustor.
 16. The method of claim 15, further comprising: passing saidcombustible gas from said scrubber to a finisher; passing waste liquidfrom said finisher to said recycler; and passing said waste liquid fromsaid recycler to said combustor.
 17. The method of claim 10, whereinsaid one or more filters comprise one or more catalysts.
 18. The methodof claim 10, wherein said one or more filters comprise one or moreliquids.
 19. A combination, comprising: a combustor having an upperouter wall portion and a lower base portion; an inner wall disposedwithin said combustor, an upper portion of said inner wall beingconnected to said combustor to form an inner chamber and an outerchamber, a lower portion of said inner wall defining a first openingwithin said combustor; an ash support member disposed within saidcombustor below said first opening, said ash support member beingaffixed within said combustor so that ash may spill from said ashsupport member over at least approximately 80 percent of an outerperiphery of said ash support member.
 20. The combination of claim 19,wherein said ash support member is affixed within said combustor so thatash may spill from said ash support member over at least approximately90 percent of said outer periphery of said ash support member.
 21. Thecombination of claim 19, further comprising: a first agitating memberdisposed within said combustor above said opening; and a secondagitating member disposed within said combustor below said opening. 22.The combination of claim 21, further comprising a third agitating memberdisposed within said combustor above said opening.
 23. The combinationof claim 19, further comprising: a scrubber, said scrubber beingoperably connected to said combustor to provide a flow path from saidouter chamber of said combustor to said scrubber; a finisher, saidfinisher being operably connected to said scrubber; and one or morefilters disposed in said finisher.
 24. The combination of claim 19,further comprising: a blower disposed downstream from said combustor andoperably connected to said combustor for withdrawing a combustible gasfrom said combustor, said blower comprising: an impeller housing; animpeller disposed within said impeller housing; and a seal betweenportions of said impeller housing.
 25. The combination of claim 24,wherein said blower further comprises: a shaft affixed to said impeller;and at least two sets of bearings operably connected to said shaft.